It is proposed to study the role of adrenal corticol cytochrome P-450 enzymes in the control of glucocorticoid and mineralocorticoid biosynthesis. The method by which cholesterol side chain cleavage is activated by ACTH will be examined in several projects: (1) in which the circadian rhythm of corticosterone will be used as a means of examining low and high activity of the glucocorticoid pathway, (2) in which we will attempt to demonstrate that ACTH stimulates the phosphorylation of a specific factor involved in the activation of cholesterol side chain cleavage, and (3) in which we will examine the activation of cytochrome P-450scc in a cortisol secretor, the guinea pig. In a related project, the control of aldosterone biosynthesis will be examined and the influence of several agents on the cytochrome P-450scc and cytochrome P-45018 of the zona glomerulosa studied. The techniques to be applied in these studies are those developed by us for examining the interaction of substrates such as cholesterol and corticosterone with the cytochrome P-450 systems of the adrenal cortex. A combination of light absorption spectrophotometry and EPR spectroscopy will be used.